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Neuromuscular Junction Syndromes and Ocular Myopathies
Published in Vivek Lal, A Clinical Approach to Neuro-Ophthalmic Disorders, 2023
In MG, infusion of intravenous edrophonium chloride (commonly known as the Tensilon test16) inhibits activity of the acetylcholinesterase, resulting in an increase in acetylcholine concentration at the synaptic cleft and improvement of the previously deficient muscular function. If the motor deficit is unequivocally reversed after edrophonium infusion, the test is considered as “positive,” indicating a high likelihood of OMG. False-positive results have been described in botulism, Guillain-Barre syndrome as well as in other conditions. The sensitivity of the test is considered as high as 90% for MG, when considering ptosis reversal. This test requires an objective evaluation of the improvement, and therefore, the amount of ptosis/ocular misalignment should be documented photographically “before” and “after” the injection. Edrophonium has a quick, short-acting effect: its action begins within the first minute after injection, lasting 5–10 minutes.
Clinical Toxicology of Snakebite In Africa and The Middle East / Arabian Peninsula
Published in Jürg Meier, Julian White, Handbook of: Clinical Toxicology of Animal Venoms and Poisons, 2017
All patients with neurotoxic symptoms should he given a “Tensilon” (edrophonium) test as in the case of patients with suspected my asthenia gravis. Atropine sulphate (0.6 mg for adults, 50 μg/kg for children) is given by intravenous injection to block the muscarinic effects of acetylcholine. This is followed by edrophonium chloride (10 mg in adults, 0.25 mg/kg in children) by slow intravenous injection. The response should be assessed objectively. Those who respond convincingly can be maintained on neostigmine, methyl sulphate and atropine sulphate.
Myasthenia gravis
Published in Hemanshu Prabhakar, Charu Mahajan, Indu Kapoor, Manual of Neuroanesthesia, 2017
Prasanna U. Bidkar, Lakshmi K. Narmadha
Edrophonium chloride has rapid onset (within 30 s) and short duration (5 min) of action which is administered intravenously. It increases the concentration of acetylcholine by inhibiting acetylcholinesterase at the NMJ, thus improving muscle weakness. If the muscle strength improves, the test results are considered positive. Development of increased weakness suggests abnormal neuromuscular transmission. Hence, resuscitation equipment and drugs should be kept ready. A total of up to 10 mg edrophonium is administered with a small dose to begin with. This is especially to avoid the muscarinic side effects of edrophonium at larger bolus doses. Side effects of edrophonium include bradycardia, increased salivation, sweating, nausea, stomach cramps, and muscle fasciculations. The sensitivity of edrophonium test is 85% for ocular MG and 96% for generalized MG.10
A Case of Recurrent Painful Ophthalmoplegic Neuropathy Successfully Treated with Beta-blocker Eye Drop Instillation
Published in Neuro-Ophthalmology, 2021
Daisuke Takemoto, Shinji Ohkubo, Sachiko Udagawa, Mondo Kuroda, Kazuhisa Sugiyama
A 14-year-old Japanese girl had left frontal headaches and vomiting, followed by drooping of her left eyelid and double vision. She had previously experienced a similar episode triggered by tympanitis at the age of 2 years. Her history included migraine and her mother also suffered from long-standing migraine. On our clinical examination, her vital signs and physical findings were normal (except for the ptosis and ocular motility disorder). Visual acuity was normal in both of her eyes. She had an oculomotor nerve palsy with ptosis of the left eye. Her external ocular movement findings are shown in Figure 1. Her pupil sizes were 3.5 mm on the right and 4.5 mm on the left. The left eye had weak direct and indirect pupillary reflexes. An edrophonium chloride test was negative.
Quantification of Cover Test Prior and Post Pyridostigmine in Diagnosis of Myasthenia Gravis
Published in Journal of Binocular Vision and Ocular Motility, 2021
Marta Saint-Gerons, Miguel Angel Rubio, Ana Martinez, Ana Matheu
A quick and accurate diagnosis of myasthenia gravis is quite relevant in order to establish a treatment but also to avoid other potentially harmful drugs. For this reason, bedside tests have been explored, such as the ice pack test or the sleep test. Edrophonium chloride test has high sensitivity and specificity,2 but is based on subjective assessments and has the potential risk of precipitating a cholinergic crisis, so atropine and resuscitation equipment should be available.
Open source modular ptosis crutch for the treatment of myasthenia gravis
Published in Expert Review of Medical Devices, 2018
Trust Saidi, Sudesh Sivarasu, Tania S. Douglas
Globally, MG is a relatively rare disease as it affects about 3–30 per 100,000 persons depending on geographic location [13,14]. The incidence of the disease is increasing and has more than doubled in the last 20 years in Western countries as well as in Japan and Taiwan [1,15,16]. This is most likely to be a result of improved diagnosis [16] and greater ability of neurologists to differentiate MG symptoms from classical fatigue due to aging [1]. Diagnosis of the disease can be done by the ice or ice pack test, a clinically simple, safe, and affordable procedure for the diagnosis of ocular MG [17,18]. Myasthenic ptosis is known to improve with cold, and therefore, the ice pack test is used as a tool for differential diagnosis [19]. The test is conducted by placing a surgical glove filled with crushed ice on the more ptotic eyelid for about 2 min and evaluating the effect of ice application on the ptosis [20,21]. If the disease is present, the ptosis is substantially diminished (>5 mm) and this is used to distinguish MG from other causes of ptosis or ophthalmoparesis [22]. Repetitive nerve stimulation is another method used to diagnose neuromuscular junction disorders associated with MG [23–25]. It involves electrical stimulation to a motor nerve several times per second followed by assessment for a neuromuscular junction disorder [26–28]. A decremental response of ≥10% between the first and fifth compound muscle action potential is suggestive of the presence of MG [29]. Edrophonium chloride (tensilon) assists in diagnosing a muscle disorder in MG as patients who are positive for the disease show an improvement in muscular strength following administration of the drug [30,31]. Oral pyridostigmine bromide (mestinon) is undergoing clinical trials as an alternative approach for the diagnosis of MG [32,33] due to its ability to produce rapid results [34]. It blocks an enzyme that breaks down acetylcholine, the chemical that transmits signals from nerve endings to muscles, resulting in temporary improvement in weakness of the eye muscles, an indication of the presence of MG [35].